Wire is covered with zinc, commonly called galvanizing, to protect it from rusting. The length of time before wire begins to rust depends on the weather but also on the thickness of the zinc coating. More zinc means more years of service before rusting starts. Fence manufacturers and the American Society for Testing Materials have established "classes" of zinc coatings for fence wire. Class 1 has the lightest coating of zinc and Class 3 has the heaviest (two times as much, depending on the wire size). The expected life of a fence depends on many factors, but Class 3 galvanizing can easily add 5 to 10 years of life to fence wire in a humid climate like Florida's.